1. Field of the Invention
The present invention relates to a process for fabricating an SOI substrate-by subjecting a bonded wafer composed of a semiconductor wafer of an active substrate bonded on by a semiconductor wafer of a supporting substrate to PACE (plasma assisted chemical etching) process to form the active substrate into a thin film.
2. Description of the Prior Art
The demand for SOI substrates has continuously increased in recent years, in order to make integrated circuits operatable at higher speeds. Particularly, SOI substrates including active substrates which are thin films have been commonly used to make integrated circuits operate at even further higher speeds. A conventional SOI substrate including an active substrate which is a thin film is fabricated by the following steps:
(1) bonding a semiconductor wafer of an active substrate 11 and a semiconductor wafer of a supporting substrate 12 to form a bonded wafer 14 (referring to FIG. 2a); PA1 (2) L-shaped-grinding the peripheral edge of the active substrate 11 of the bonded wafer 14 (referring to FIG. 2b); PA1 (3) alkaline etching the L-shaped-grinded bonded wafer 14 to remove the surrounding oxide film 13 and the non-attached portion of the peripheral edge (referring to FIG. 2c); PA1 (4) surface grinding the alkaline etched. active substrate 11 of the bonded wafer 14 to reduce the thickness of the active substrate (referring to FIG. 2d); PA1 (5) polishing the surface ground active substrate 11 to further reduce its thickness (referring to FIG. 2e); and PA1 (6) PACE processing the polished active substrate 11 to form the active substrate into a thin film (referring to FIG. 2f).
However, the above-mentioned process suffers from the disadvantage that it is difficult to control the etching rate, and at a peripheral edge of the substrate scratches are formed easily.
In addition, the lead time required for L-grinding and alkaline etching is too long, thus the output of the fabrication quantity is limited, resulting in unsatisfactory efficiency.